Ontogeny of swim performance and mechanics in bottlenose dolphins (Tursiops truncatus).

Morphological and physiological development impacts swimming performance throughout ontogeny. Our investigation of the ontogeny of swim performance (mean and maximum swim speed) and swim effort (stroke amplitude and tailbeat frequency) of independently swimming bottlenose dolphins (Tursiops truncatus) demonstrated that swimming capabilities are extremely limited in calves. Mean and maximum swim speeds of 0-1-month-old calves were only 37% and 52% of that for adults, respectively, and levels similar to those of adults were not achieved until one year post-partum. Limitations in swim speed were associated with an inability to achieve mature thrusting capabilities, as stroke amplitude and distance covered per stroke remained significantly lower than adult levels during the first-year post-partum. Although calves were expected to require less thrusting power to propel their smaller bodies through water, size-specific stroke amplitudes of 0-3-month-olds (23-26% of body length) were smaller than those of dolphins >or=10 months post-partum (29-30% of body length). As a result, swim speed standardized by body length was significantly slower for 0-3-month-old dolphins compared with dolphins >or=10 months post-partum. These results suggest that other factors, such as underdeveloped physiology, act synergistically with small body size to limit independent swim performance in dolphins during ontogeny.